P1420: PRE-CLINICAL PROOF OF CONCEPT DEMONSTRATES ROBUST ACTIVITY OF UCART20X22 DUAL CAR T-CELLS FOR THE TREATMENT OF B-CELL MALIGNANCIES
Authors: B. Aranda Orgilles, I. Chion-Sotinel, S. Grudman, B. Mumford, C. Dixon, P. Duchateau, R. Galetto, A. Gouble, L. Poirot
Journal: HemaSphere (2022)

Background: Autologous CAR T-cell therapies have been transformative in the treatment of selected blood cancers. Despite this remarkable success, long term studies on patients treated with CD19 or CD22 CAR T-cells revealed the emergence of relapses that can be due to antigen loss. The therapeutic options after CAR T-cell relapses are limited, underscoring the urgent need to develop novel therapies to improve current survival rates. In addition, there is a need to develop allogeneic "off-the-shelf" therapies that are readily available at the time of treatment decision and that overcome development limitations of current autologous approaches. Aims: To develop efficient dual allogeneic CAR T-cells with the potential to overcome current challenges in the treatment of B-cell malignancies. Methods: We generated UCART20x22, allogeneic CAR T-cells targeting CD20 and CD22, using a bicistronic lentiviral construct to express both CARs. TALEN® gene editing technology was used to mediate inactivation of the TRAC and CD52 genes: TRAC KO is used to prevent Graft-vs-Host Disease, and CD52 KO to allow deeper host lymphocyte depletion by conferring resistance to lymphodepletion regimens including an anti-CD52 monoclonal antibody, such as alemtuzumab. To test UCART20x22 activity, we use a combination of in vitro cytotoxicity assays against tumor cell lines, along with pre-clinical in vivo models assessing efficient dose/response and recapitulating antigen escape. We also performed in vitro activity assays against primary non-Hodgkin Lymphoma cells expressing different levels of the targeted antigens. Results: We demonstrate that UCART20x22 displays strong activity against tumor cell lines expressing either a single antigen, CD20 or CD22, or both simultaneously. UCART20x22 also specifically releases IFNg in response to antigen specific stimulation. We also show that the specific activity of UCART20x22 persists over time against tumor cells expressing either one or both antigens. Our preclinical models illustrate that UCART20x22 dual CAR T-cells provide efficient in vivo clearance of tumor cells in a dose dependent manner. UCART20x22 efficiently eradicates tumors expressing both or a single antigen, and we observe persistence of UCART20x22 cells in the bone marrow after tumor clearance. Furthermore, in vitro assays against primary cells from Non-Hodgkin Lymphoma patients with diverse CD22 and CD20 antigen levels demonstrate that UCART20x22 has potent and specific cytotoxic activity as well as IFNg release against these panel of samples. Summary/Conclusion: We present a robust pre-clinical proof of concept of a potent allogeneic dual CAR T-cell product candidate, UCART20x22, with the potential to 1) overcome common mechanisms of resistance in B-NHL, 2) enable the development of allogeneic CART option for B-NHL patients, 3) reduce the time from treatment decision to infusion.